Field of the Invention
Apparatuses consistent with the present disclosure relate to a transformer and an LLC resonant converter having the same, and more particularly, to an LLC resonant converter including only one magnetic element without adding external elements for resonance in the LLC resonant converter.
Description of the Related Art
In order to implement a high power density power source, an LLC resonant converter which may perform a zero voltage switching (ZVS) operation in a full load region and is advantageous in a high frequency driving is used. The LLC resonant converter allows a switching frequency and a resonance frequency to operate at the same point by a ratio of the number of turns of a transformer and an appropriate design of a resonance capacitor, a resonance inductor, and a magnetized inductor which are essential elements for a resonance operation to minimize a variation of an operation frequency for a wide load variation, thereby securing a stable operation and control. The resonance inductor is generally implemented as a leakage inductor of the transformer.
As a size of the transformer is reduced and elements for implementing a high power density power conversion apparatus are integrated, leakage inductance which may be used as the resonance inductor is not often sufficiently secured. In particular, in a case in which a planar transformer rather than a general winding type transformer is used to further reduce a physical size of the transformer, since the leakage inductance is small in the order of several tens to several hundreds of nH, a separate external inductor is required to secure the resonance inductor. As a result, due to an increase in a size of a system and an increase in the number of parts, it is difficult to implement the high power density power conversion apparatus.